The present invention relates to a housing suitable for a high-frequency electronic device such as, for example, a down converter for receiving satellite broadcasting.
A conventional housing for a high-frequency electronic device will be described below with reference to FIGS. 8 to 11. FIG. 8 is a perspective view of a frame used in the conventional housing, FIG. 9 is a perspective view of a cover for covering an opening of the frame shown in FIG. 8, FIG. 10 is a sectional view of principal portions, explaining how to engage the frame and the cover with each other, and FIG. 11 is a sectional view of principal portions, explaining a problem involved in the conventional frame-cover engagement.
In FIG. 8, the frame 31 comprises a receptacle portion 32 for receiving therein a circuit board (not shown) with electronic circuits formed thereon and a feed horn 33 for introducing a signal from a broadcasting satellite into the interior of the frame, the receptacle portion 32 and the feed horn 33 being formed as an integral body by die casting of aluminum. Terminals 34 as outlets of output signals after frequency conversion are attached to a side face of the receptacle portion 32. Inside an opening brim of the receptacle portion 32 is formed an engaging portion 38 to which a cover 37 shown in FIG. 9 is to be applied, the engaging portion 38 comprising a vertical plane 35 and a horizontal plane 36. The cover 37 is brought into engagement with the frame 31 to constitute a housing for a high-frequency electronic device.
The cover 37 shown in FIG. 9 is formed by subjecting a stainless steel plate to press working. The cover 37 comprises an expanded portion 39 having a flat central part and an inclined portion 39a formed along the marginal portion of the expanded portion 39. In the inclined portion 39a, first engaging pawls 40 and second engaging pawls 41 for engagement with the engaging portion 38 of the frame 31 are formed in an alternate manner. The first engaging pawls 40 extend longer than the second engaging pawls 41 directly from the inclined portion 39a.
The second engaging pawls 41 extend from the inclined portion 39a in parallel with the surface of the expanded portion 39. When the first and second engaging pawls 40 and 41 are engaged with the engaging portion 38 of the frame 31, the second engaging pawls 41 are in surface contact with the horizontal plane 36 of the engaging portion 38, while the first engaging pawls 40 are in surface contact with the horizontal plane 36 and their tips bite into the vertical plane 35 and are thereby engaged with the same plane.
A method for engaging the frame 31 with the cover 37 will now be described with reference to FIG. 10. First, the cover 37 is put on the horizontal plane 36 of the engaging portion 38 of the frame 31. In this state, the first engaging pawls 40 are inclined relative to the horizontal plane 36 and their tips are in abutment onto the horizontal plane 36. On the other hand, the second engaging pawls 41 are parallel to the horizontal plane 36 at a position higher than the horizontal plane 36. Next, a press 43 having pressing portions 42 correspondingly to the marginal portion of the cover 37 is brought down from above the cover 37, allowing the pressing portions 42 to press the first and second engaging pawls 40 and 41 of the cover 37. As a result, the first engaging pawls 40 are bent and extended at their base positions in parallel with the surface of the expanded portion 39 and their tips slide on the horizontal plane 36 toward the vertical plane 35 until they finally bite into the vertical plane 35 and are thereby engaged with the same plane.
In the above conventional housing, however, when the cover 37 is placed on the horizontal plane 36 of the engaging portion 38 of the frame 31, the first engaging pawls 40 are inclined relative to the horizontal plane 36 and their tips are in abutment with the horizontal plane obliquely, with the angle Ka (see FIG. 10) between the horizontal plane 36 and the first engaging pawls 40 Fez being large. Consequently, when the first and second engaging pawls 37 and 40 of the cover 37 are pressed by the pressing portions 42 of the press 43 to bend and extend the first engaging pawls 40, as shown in FIG. 11, the tips of the first engaging pawls 40 are difficult to slide on the horizontal plane 36 and bite into the horizontal plane, not into the vertical plane 35, resulting in that the engagement between the frame 31 and the cover 37 becomes incomplete.